I had the same issue. I was able to fix the problem by entering a few simple commands (shown below). Note this process will reset MATLAB's path settings to factory default, so you may want to backup your current path like so:
>> savepath([pwd filesep 'pathbackup.m'])
To fix the warning message issue, enter the following commands...
>> rehash toolboxcache
The exit command will close MATLAB. After the program shuts down, restart MATLAB; the warning message should no longer appear. Upvote if it works! Comment if not!